Method of generating highpressure steam



Sept. 4, 1934. E. PFLEIDERER METHOD OF GENERATING HIGH PRESSURE STEAK Filed 0012. 3. 1931 2 Sheets-Sheet 1 Y u. v r

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Sept. 4, 1934. E. PFLEIDERER METHOD 0F GENERATING HIGH PRESSURE STEAK Filed Oct. 3. 1931 2 Sheets-Sheet 2 wwf, .w

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Patented Sept. 4, 1934 PATENT OFFICE METHOD OF GENERATING HIGH- vPRESSURE STEAM:`

Ernst Peiderer, Ludwigshafen-on-the-Rhine, Germany Application October 3, 1931, Serial No. 566,671 In Germany October 13, 1930 1 Claim.

This invention has for its object a new method of producing steam of highest pressure. The essential feature of this method resides in the use of superheated steam for heating of the feed 5 water to thetemperature of the saturated steam. The boiler of the saturated steam has only the function of transmitting of the heat of evaporation to the water, While the Iheat of liquid is derived wholly or almost wholly from the superheated steam or the superheater. 'I'his method affords several advantages. The superheater is exposed to the hottest gases and the steam-generator is arranged behind the superheater. 'Through the superheater ows steam only so that no scale is deposited therein. The tubes of the superheater can therefore be subjected to the limit of allowed stresses. On the other hand the dimensions of the boiler itself may be small as it has only to transmit the heat of evaporation. It is alsdan importantfeature of the new method that it makes possible to keep the superheat of the steam used on a constant temperature, while hitherto this has been impossible inasmuch as the proportion of the heating surface of the boiler and the superheater remain the same while the load, the temperature of the combustion chamber, the kind of the coal and so on are constantly chang- In the drawings two embodiments of the invention are illustrated.

Fig. 1 shows one embodiment and Fig. 2 another embodiment.

Fig. 3 shows a somewhat different mode of preheating of the water.

Referring rst to Fig. 1 the combustion chamber a is heated by coal dust. b are the dustbumers and c the superheating tubes only one of which is shown. The steam of the steam-drum d is fed into the superheater. This drum, the tubes i and the drums k form a vertical boiler. The

combustion gases pass from the chamber a through the flue g to the water-tubes i. The water is preheated, for instance to a temperature of 200 C., in the known manner by means of an economizer or a regenerative preheating, it means by steams derived from the turbine. It is then led into a supplementary. receptacle m. Into the same receptacle superheated steam is supplied through the pipe n. Thissuperheated steam gives olf to the water the liquid heat corresponding to the pressure prevailing in the receptacle m. The feed water thus heated is pressed by means of the pump o into the steam-drum d directly or through the tube-coil h arranged in the flue of the gases between the superheater c and the boiler. The tube n leading superheated steam into the receptacle m is branched off from the tube leading from the supplementary superheater p into the engine. 'Ihe nest of the tubes i is so dimensioned as to easily afford the heat of evaporation which is very small with high pressures,

f. i. 146 units of heat for 200 atmospheres. In the drum d van appreciably higher pressure is generated than is necessary in the engine for instance a 5-20% higher pressure. This pressure 65 diminishes while passing through the superheaters c and p to the engine for about 5-20 atmospheres. By this fall of pressure it is obtained, that the steam uniformly flows through the superheater tubes and that the latter are intensively'70 cooled. As mentioned a part of the steam is used for heating of the water in the receptacle or the drum m. By these means it is obtained that almost the whole liquid heat necessary for the steam is supplied by the heat accumulated in the steam in the superheater. In the tubes exposed to the greatest stresses flows steam only and more steam than is consumed by the engine. This steam does not deposit any scale and every tube is positively and uniformly cooled.

In some cases it may be of advantage to arrange between the combustion chamber a of the superheater c and the boiler i, d, 1c, a supplementary combustion chamber e with burners f, as illustrated in Fig. 2. By these means it is possible to control the proportion of the temperatures in the superheater and in the generator of the saturated steam. When starting with heating it is possible to operate at first the burners only, while the burners b are brought into operation later on when the boiler is connected to the main steam line. The burners f are therefore destined for the saturated-steam boiler only and their operation may be diminished or altogether shut out.

According to the modification shown in Fig. 2 not a part of the steam coming from the superheater c but the whole steam heated to 450500 C. is led into the feed water receptacle m. It loses here its superheat and leaves as saturated 100 steam into the second or the supplementary superheater p, where it is again superheated to a temperature needed in the engine f. i. to 450 C.

This modification has several advantages over the first described method. According to the first method the boiler for the saturated steam must generate not only the steam needed by the engine but also the part ofthe steam which is condensed in the receptacle m. 'Ihe boiler must therefore generate more steam than in the second arrangement according to which no steam or only a very small quantity of it is condensed in the drum m because not a part of the steam but.

the Whole steam is led into the drum m. With suiclently superheated steam even additional steam may be generated in the drum m. Thus as much as possible of heat is derived from the combustion gases as a superheat, While the heating surfaces in contact with water take a relatively very small quantity of heat from these gases.

A further advantage of the method according to Fig. 2 resides in the fact, that the steam in the rst superheater can be heated to a higher degree than needed in the engine. F. i. the engine can use a steam of maximum 450 C., while the superheater is able to develop a temperature of 500 C. or even more. With the arrangement described it is therefore possible to develop in theA rst superheater a higher temperature than can be used in the engine. For every kilogram of steam used in the engine more heat can be introduced into the drum m than in the case of limiting the temperature in the superheater f. i. to 450 C. This fact is of great importance with high pressures because the liquid heat grows with the pressure.

A third advantage of the last named method lies in the fact that it is now easily possible to regulate the temperature oi the steam introduced into the engine. y The superheat of the steam depends upon the temperature of the feed water. Assuming that the latter is heated by the regenerative system r1, r2 and the preheating steam of the last degree r2 is diminished the following changes will arise.

With the same load of the engine the latter will consume less steam than before, because the part of the steam which is condensed has now become greater. The immediate eiect of the diminishing of the steam consumed is that the pressure rises and the combustion is to be relaxed. After a short time owing to the lower temperature of the feed water more steam will be bound in the supplementary drum for preheating of the water. The pressure will diminish. 'I'he combustion is then increased. After a permanent Working is arrived at, it will result that the decrease of the thermal efciency by diminishing the quantity of steam derived from the turbine for preheating makes it necessary to generate more heat in the boiler and in the superheater for the same load. More heat will be passed through the boiler and the rst superheater. But in the second superheater less steam will flow so that the superheating eiect on this steam is increased before it enters the turbine s.

The steam supplied to the turbine can therefore be regulated in an automatic way by a thermostat acting upon the inlet valve v of the last part of the regenerative preheating system. This can be done for instance in the manner shown in Fig. 2. The thermostat t acts upon the diaphragm y which moves a needle directing a stream of pressure-oil to one or the other side of the piston a controlling the position of the valve 'v According to the modification shown in Fig. 3 the feed water is heated indirectly by the superheated steam. The water flows through the container m accommodating the coil c of the superheated steam. This steam may then be led through a second superheater in order to obtain the temperature needed in the engine.

What 'i' claim is:

A method of generating high-pressure steam in a steam power plant, which comprises preheating the feed water first by means other than fresh superheated steam and then by fresh superheated steam, and controlling the preheating by the rst named means by means responsive to the temperature of the steam supplied to the consumer,

ERNST PFLEIDERER. 

